This invention relates to an improved aqueous dispersion of alumina and a silicone resin.
Open-celled porous ceramic structures are useful for diverse applications such as catalyst supports and as heat-resistant filters for molten metals. Such structures can be formed by mixing together a ceramic material and a binder, saturating a porous material with the binder, and heating the saturated material to a temperature sufficient to vitrify the ceramic material and to destroy the porous material. For example, U.S. Pat. No. 3,090,094 discloses a method for producing such an article. A slurry of a finely divided ceramic powder and a ceramic binder is produced and a polyurethane sponge is immersed in the slurry. The saturated sponge is then heated to a temperature of about 2500.degree. F. to burn out the sponge and to vitrify the slurry into an open-celled ceramic material.
U.S. Pat. No. 3,090,691 discloses mixing together a silicone resin and a volatile-free ceramic material under heat and pressure to form a coherent mass and heating the mass to obtain a ceramic article.
In commonly assigned application Ser. No. 571,602 filed Apr. 25, 1975 a method for producing a cellular ceramic catalyst support is disclosed. The method comprises impregnating an organic sponge flocked with wood or textile fibers with a slurry of alumina and a silicone resin, the latter being a phenyl lower alkyl silicone resin dissolved in an organic solvent. The viscosity of this slurry can be decreased by addition of a compatible organic thinner such as toluene, xylene, an alcohol or a chlorinated solvent. As disclosed, the support consists of a random-fiber ceramic framework with a high surface area which can be glazed and plated to function in catalytic reactions. The organic slurry can be used, with difficulty, to saturate, for example, a polyurethane sponge. The organic solvent not only makes impregnation difficult; it is also undesirable because of the volatility of the solvent and the danger posed by the vapors produced when the sponge saturated with the slurry is subjected to a high temperature sintering operation.